Utilization of petroleum refinery gas



April 27, 1943. E. B. HJERPE ET AL 2,317,603

UTILIZATION OF PETROLEUM REFINERY GAS Original Filed March 25, 1936 COMPRESSOR Q 1 ll HEATER, 4 W 5 cozvoszvsze PUMP CHAMBER 7 DE) GAS 70 TEMPERAfi/I? 72 CONTROL LOW BOILING I NAPHTHA TEMPERATURE g CONT EOL.

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Patented Apr. 27, 1943 2,317,803 I UTILIZATION OF rggi tomum REFINERY Eric B. Hjerpe, Port Arthur, Tex., and William A.

Gruse, Wilkinsbnrg, Pa., assign era to Gulf Oil Corporation, Pittsburgh, Pa., a corporation of Pennsylvania Original application March 25, 1936, Serial No. 70,856. Divided and this application August 8, 1938, Serial No. 223,760

2 Claims. (Cl. 196-10) This invention relates to utilization of petroleum refinery gas; and it comprises a process wherein a petroleum refinery gas containing butylenes is fractionated to separate a fraction containing only butylenes and constituents slightly higher boiling than butylenes, wherein the fraction so separated is subjected to a temperature and a pressure sufiicient to polymerize the butylenes and other components of the fraction to products having a boiling point within the range of gasoline boiling points; all as more fully hereinafter set forth and as claimed.

The present application is a division of our prior copending application Serial No. 70,856, filed March 25, 1936, which is in part a continuation of our prior application Serial No. 613,774, filed May 26, 1932, now U. S. Patent No. 2,099,480, patented November 16, 1937.

In the cracking of petroleum, decomposition occurs with the formation of components of less complexity from those of greater complexity. In addition, saturated hydrocarbons are converted into unsaturates. Most petroleum cracking is directed toward the formation of gasoline, but decomposition products are invariably formed which are too low boiling to be included in commercially acceptable gasoline.

Among the decomposition products arising from the cracking of petroleum are the aliphatic hydrocarbons having four carbon atoms. Large quantities of butylenes are produced, and on.

account of the low boiling point and high vola tility of this fraction, in many cases the butylenes cannot be retained in the gasoline fraction; large quantities of the butylenes must therefore be allowed to'escape as free gas or used as fuel.

We have discovered that the butylenes may be separated from the bulk of refinery gases together with components of approximately the same boiling point range and the entire fraction so separated utilized to great advantage by subiecting it to polymerization. We have found that such polymerization, when properly controlled,

will yield products boiling within the gasoline boiling point range and, in addition, such products will be characterized by remarkably high anti-knocking tendencies. The products are useful either alone as special fuel or for blending with other gasoline to decrease the knocking characteristics of the latter.

According to our invention, a refinery gas containing butylenes is subjected to fractionation to recover therefrom a fraction containing the butylenes together with other components of nearly the same boiling point range such as the butanes. We term this the C4 cut." This 04 cut may be removed from the bulk of the refinery gases by any of several methods, such as fractional liquefaction of the gas or by more or less complete liquefaction followed by fractional distillation, etc. Advanta'geously, a method is chosen which best fits in with the independent treatment of other of the gas constituents such as the amylenes, propane, and

propylene, etc. Such a method is described in our parent application serial No. 613,774 wherein part of the C4 cut is obtained as an overhead from gasoline condensed under pressure, while the remainder is obtained as a liquid residue after removal of lower boiling fractions from a liquefied light fraction of gas.

In accordance with one embodiment of the invention,-the C4 cut is subjected to controlled temperatures and pressures suficient to cause polymerization of some or all of its components with the ultimate production of a liquid polymer boiling within the range of gasoline boiling points. If polymerization is carried too far, the product is too high boiling and if not carried far enough, the yield becomes unprofitable. Within limits, the velocity of polymerization varies directly as the temperature and directly as the pressure according to known chemical laws. That is to say, for a given velocity of reaction, if the pressure is raised, the temperature may be lowered; and if the temperature is raised, the pressure may be lowered.

In the absence of catalysts, we find that convenient conditions under which to polymerize the C4 out are temperatures of about 350 C. and pressures sumcient to cause the reaction to Proceed at a practical velocity which, at the stated temperature, would be approximately 1000 lbs. per square inch. Much lower pressures may be used if desired, but at the stated temperature the reaction proceeds somewhat more slowly. This may be compensated for, at least in part, by raising the temperature. We find that polymerization may be readily accomplished at temperatures under 350 6., although the velocity of reaction is less. Again we may compensate for this by increasing the pressure.

The accompanying drawing illustrates diagrammatically a specific embodiment of the invention. In the drawing, the single figure is a fiow sheet illustrating process steps for thermal polymerization, in accordance with our invention.

Referring to the drawing, reference character I indicates a stream of starting stock which may be, for instance, the gases from a "stabilizer or- "debutanizer in which raw pressure distillate or compression gasoline is weathered or stabilized. These gases are sometimes termed debutanizer gas. They comprise largely the aliphatic hydrocarbons of the C4 group and usually contain varying amounts of butane-1, butene-2, and isobutene as well as butanes. Stream l enters a compressor 2 wherein it is subjected to any pressure desired during subsequent operations. From the compressor 2, the stream l is conveyed through a heater il wherein the constituents are brought to the desired'temperature. Leaving the heater, the stream enters either valved line 4 leading to a catalyst chamber 5 or valved by-pass line. f circumventing the catalyst chamber. Catalyst chamber 5 is located in a temperature maintaining chamber I by means of which the temperature of the catalyst chamber may be controlled within narrow limits. Leaving the catalyst chamber 5, or by-pass line 6, the stream of polymerized material enters a condenser 9 wherein the products of polymerization are cooled. From condenser 9, the products are transferred through line In and pump II to a fractionating tower i2 where the products are subjected to any desired fractionation and the permanent gases removed. Tower I2 is equipped for removal of various fractions as side streams. Accurate control of the fractionation is facilitated by temperature control elements l3, I4- and i5. .Advantageousaly, we control the temperatures within the tower 12 so as to remove at one level a product of motor gasoline boiling range and to remove at another level a lower boiling product suitable for use as a blending naphtha. Any material boiling over the gasoline range may be withdrawn through line I6, and residual gases leave the tower through conduit I1. Our process is usually so conducted as to produce a minimum of residual gases and a minimum of polymers higher boiling than gasoline. The low boiling naphtha removed as a side stream is of high octane number and makes an excellent product for blending with motor fuels of lower octane number andof lower volatility. The motor gasoline is likewise of high octane number and may be used as a special premium motor fuel or as a blending agent for raising the antiknock characteristics of other gasolines.

In the heater coil 3 the gas is heated to a temperature of 350 C. and polymerized, after which the products are conveyed directly to the condenser 9 through by-pass line 6.

The invention is not to be considered as limited with regard to any particular way of fractionating the polymer produced. The figure simply illustrates an advantageous way of finishing the unfractionated product.

Others in the prior art have proposed to subject various gaseous hydrocarbons and gas fractions to high temperatures, in excess of 1200 F.,

to crack the same and occasionally (when long times of contact are employed) to produce aromatic oils, such as benzol and toluol. Such op erations are sometimes referred to as "polymerizing" operations, although the terms "gas Pyrolysis" and gas cracking are to .be preferred. In any event, our process does not contemplate the use of such temperatures, which are neither necessary nor desirable when converting gases predominating in butane and butylene to gasoline-like hydrocarbons, as distinguished from aromatics.

Weare also aware that it has been proposed to polymerize various olefin-containing gases, or pure olefins, at temperatures between about 200 and 400 0., in the presence of oxygen. Our invention does not however contemplate the use of oxygen for the deliberate purpose of affecting the reactions taking place, nor is such use intended to becovered by the term "polymerization" as employed herein.

What we claim is:

I. In the manufacture of gasoline-like hydrocarbons of high anti-knock value when used as motor fuel, from normally gaseous hydrocarbons produced in cracking petroleum oils by subjecting such normally gaseous hydrocarbons in the absence of a catalyst to elevated temperatures and pressures effective to polymerize normally gaseous constituents to low-boiling, normally liquid products, the improvement which comprises subjecting a fraction consisting predominantly of saturated and unsaturated hydrocarbons having four carbon atoms per molecule, containing relatively small amounts of hydrocarbons having three carbon atoms per molecule but substantially free from more refractory hydrocarbons such as methane, ethane and ethylene, to a polymerizing temperature of the order of 350 C. and a pressure of about 1000 pounds per square inch.

2. In the manufacture of gasoline-like hydrocarbons of high anti-knock value when used as motor fuel, from normally gaseous hydrocarbons such as those produced in cracking petroleum oils, by subjecting such normally gaseous hydrocarbons in the absence of a catalyst to elevated temperatures and pressures effective to polymerize normally gaseous constituents to low-boiling, normally liquid products, the improvement which comprises subjecting to said polymerizing temperatures and pressures a fraction consisting predominantly of saturated and unsaturated hydrocarbons having four carbon atoms per molecule, containing relatively small amounts of hydrocarbons having three carbon atoms per molecule, but

. substantially free from more refractory hydro- ERIC B. HJERPE. WILLIAM A. GRUSE. 

